1. Field of the Invention
The present invention relates to a method of estimation and of hierarchised coding of the motion of image sequences, used in particular in image transmission apparatuses with a view to decreasing the information rate.
2. Discussion of the Background
A method and a device for estimation and hierarchised coding of the motion of image sequences have been proposed in French Patent Application No. 89 11328 filed in the name of THOMSON CONSUMER ELECTRONICS, which corresponds to U.S. patent application Ser. No. 07/678,278, now allowed. This method is characterised in that it consists, at a first level, in partitioning the current image into macroblocks of 2.sup.p+1 .times.2.sup.p+1 pixels and in determining a first motion-vector field associated with this division into macroblocks, by using an iterative and recursive estimation algorithm initialised with motion vectors estimated for the previous image, then, at a second level, in partitioning each of the macroblocks into quadrants and in determining, for the blocks which result therefrom, a second motion-vector field by using the same estimation algorithm but initialised with vectors from the field of motion which were estimated at the previous level, then at i.sup.th level, i=3 to p, in partitioning each of the blocks considered at level i-1 into quadrants and in determining, for the blocks which result therefrom, an i.sup.th motion-vector field by using the same estimation algorithm initialised with the vectors from the field of motion which were estimated at the previous level, the blocks of minimum size being blocks of 2.sup.1+1 .times.2.sup.1+1 pixels, and in determining a final motion-vector field from the p resulting motion-vector fields by choosing the lowest level of division for which the motion vector associated with the corresponding block leads to the minimisation of a criterion expressing the differences in luminance between blocks corresponding in the successive images through the estimated displacement vectors.
This process of estimation makes it possible to enhance the convergence of the recursive motion-estimation algorithm used and makes it possible optimally to adapt the motion-estimation algorithm to the "Quadtree" type coding which will be done subsequently of the resulting motion field.
This process of estimation can be used, among other things, in the context of HD-MAC.